Human trophoblast stem cells and and methods of therapeutic screening

ABSTRACT

Existence of human trophoblast stem (hTS) cells has been suspected but unproved. The isolation of hTS cells is reported in the early stage of chorionic villi by expressions of FGF4, FGFR-2, Oct4, Thy-1, and stage-specific embryonic antigens distributed in different compartments of the cell. hTS cells are able to derive into specific cell phenotypes of the three primitive embryonic layers, produce chimeric reactions in mice, and retain a normal karyotype and telomere length. In hTS cells, Oct4 and fgfr-2 expressions can be knockdown by bFGF. These facts suggest that differentiation of the hTS cells play an important role in implantation and placentation. hTS cells could be apply to human cell differentiation and for gene and cell-based therapies.

CROSS REFERENCE

This application is a divisional application of U.S. patent applicationSer. No. 13/415,595, filed on Mar. 8, 2012, now U.S. Pat. No. 8,497,120,which is a divisional application of U.S. patent application Ser. No.12/972,237, filed on Dec. 17, 2010, now U.S. Pat. No. 8,163,553, whichis a divisional application of U.S. patent application Ser. No.12/405,112, filed Mar. 16, 2009, now U.S. Pat. No. 7,892,534, which is adivisional of U.S. patent application Ser. No. 11/361,588, filed on Feb.24, 2006, now U.S. Pat. No. 7,642,091, which claims priority to U.S.Provisional Patent Application Ser. No. 60/655,747, filed on Feb. 24,2005.

SEQUENCE LISTING

The instant application contains a Sequence Listing that was originallyfiled on March 10, 2011 in grandparent application Ser. No. 12/972,237,which was submitted in ASCII format via EFS-Web and is herebyincorporated by reference in its entirety. Said ASCII copy, created onFeb. 18, 2011, is named 38219-701-402_Seq_Lstg.txt and is 11 Kilobytesin size.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an isolated preparation of human trophoblaststem cells and use thereof.

2. Description of the Related Art

In mammals, the earliest developmental decision specifies thetrophoblast cell lineage. In mice, this lineage appears at theblastocyst stage as the trophectoderm, a sphere of epithelial cellssurrounding the inner cell mass (ICM) and the blastoceol. Afterimplantation, the ICM gives rise to the embryo proper and someextraembryonic membranes. However, the trophectoderm is exclusivelyrestricted to form the fetal portion of the placenta and the trophoblastgiant cells. The polar trophectoderm (the subset of trophectoderm indirect contact with the ICM) maintains a proliferative capacity andgives a rise to the extraembryonic ectoderm (ExE), the ectoplacentalcone (EPC), and secondary giant cells of the early conceptus. The restof the trophectoderm ceases to proliferate and becomes primary giantcells. Studies in primary culture and chimeric mice have suggested thatstem cells exist in the extraembryonic ectoderm which contributesdescendants to the EPC and the polyploid giant cells. Further evidenceindicated that maintenance of these stem cell-like characteristics wasdependent on signals from the ICM and later from the epiblast, sincediploid trophoblast cells transformed into giant cells when removed fromthe embryonic environment. However, the nature of the embryo-derivedsignal was not known and all attempts at routine long-term culture ofmouse trophoblast stem cells have been unsuccessful (U.S. Pat. No.6,330,349).

Stem cells have the capacity to divide and proliferate indefinitely inculture. Scientists use these two properties of stem cells to produceseemingly limitless supplies of most human cell types from stem cells,paving the way for the treatment of diseases by cell replacement. Infact, cell therapy has the potential to treat any disease that isassociated with cell dysfunction or damage including stroke, diabetes,heart attack, spinal cord injury, cancer and AIDS. The potential ofmanipulation of stem cells to repair or replace diseased or damagedtissue has generated a great deal of excitement in the scientific,medical and/biotechnology investment communities.

U.S. Appl. No. 2003104616 disclosures that ES cells from variousmammalian embryos have been successfully grown in the laboratory. Evansand Kaufman (1981) and Martin (1981) showed that it is possible toderive permanent lines of embryonic cells directly from mouseblastocysts. Thomson et al., (1995 and 1996) successfully derivedpermanent cell lines from rhesus and marmoset monkeys. Pluripotent celllines have also been derived from pre-implantation embryos of severaldomestic and laboratory animal species such as bovines (Evans et al.,1990) Porcine (Evans et al., 1990, Notarianni et al., 1990), Sheep andgoat (Meinecke-Tillmann and Meinecke, 1996, Notarianni et al., 1991),rabbit (Giles et al., 1993, Graves et al., 1993) Mink (Sukoyan et al.,1992) rat (Iannaccona et al., 1994) and Hamster (Doetschman et al.,1988). Recently, Thomson et al (1998) and Reubinoff et al (2000) havereported the derivation of human ES cell lines. These human ES cellsresemble the rhesus monkey ES cell lines.

ES cells are found in the ICM of the human blastocyst, an early stage ofthe developing embryo lasting from the 4^(th) to 7^(th) day afterfertilization. The blastocyst is the stage of embryonic developmentprior to implantation that contains two parts via.

1. Trophectoderm: outer layer which gives extra embryonic membranes.

2. Inner cell mass (ICM): which forms the embryo proper.

In normal embryonic development, ES cells disappear after the 7^(th) dayand begin to form the three embryonic tissue layers. ES cells extractedfrom the ICM during the blastocyst stage, however, can be cultured inthe laboratory and under the right conditions proliferate indefinitely.ES cells growing in this undifferentiated state retain the potential todifferentiate into cells of all three embryonic tissue layers.Ultimately, the cells of the inner cell mass give rise to all theembryonic tissues. It is at this stage of embryogenesis, near the end offirst week of development, that ES cells can be derived from the ICM ofthe blastocyst.

The ability to isolate ES cells from blastocyst and grow them in cultureseems to depend in large part on the integrity and condition of theblastocyst from which the cells are derived. In short, the blastocystthat is large and has distinct inner cell mass tend to yield ES cellsmost efficiently. Several methods have been used for isolation of innercell mass (ICM) for the establishment of embryonic stem cell lines. Mostcommon methods are natural hatching of the blastocyst, microsurgery andimmunosurgery.

Expression and functional analyses indicated that FGF4 and fgfr-2 may beinvolved in trophoblast proliferation. The reciprocal expression domainsof fgfr-2 and FGF4 suggested that the trophoblast could be a targettissue for an embryonic FGF signal. fgfr-2-null and FGF4-null mice showsimilar peri-implantation lethal phenotypes. This may result fromdefects in the ICM and its endoderm derivatives. However, it is alsoconsistent with the possibility that FGF4 acts on the trophoblastthrough fgfr-2 to maintain a proliferating population of trophoblastcells. Support for this latter possibility is provided by recent studiesshowing that inhibiting FGF signaling blocked cell division in both theICM and trophectoderm.

In humans, the inner cell mass (ICM) of blastocyst generates humanembryonic stem (hES) cells at the earliest stage of embryogenesis (J. A.Thomson et al., Science, 282, 1145 (1998)). The hES cells appearapproximately 4-5 days postfertilization with full self-renewal capacityand can yield all of the specialized cell phenotypes of the body. Humanembryonic germ stem (hEG) cells, which are derived from fetal primordialgerm ridge at 5-9 weeks post-fertilization, also possess pluripotency(M. J. Shambloff et al., Proc. Natl. Acad. Sci. USA, 95, 13726 (1998)).In vitro, both hES and hEG cells will spontaneously generate embryoidbodies (EBs) that consist of cell types from all three primary germlayers (M. Amit et al., Dev. Biol., 227, 271, (2000); M. J. Shambloottet al., Proc. Natl. Acad. Sci. USA., 98, 113, (2001)), giving anenormous potential to be used in cell-based therapies (K. Hochedlingerand R. Jaenisch, N. Engl. J. Med., 349, 275 (2003)).

Comparatively, research has paid less attention to the outertrophectoderm of blastocyst in humans. Most of the knowledge on hTScells has been based on experiments on mice. In mice, trophectodermalsubtypes initiate at peri-implantation to form three distinctivetrophoblast cell layers. The trophectoderm overlying the ICM continue todivide and form the polar trophectoderm, which then grows into theextraembryonic ectoderm (ExE), where a diploid cell population ismaintained with some develop into the mature chorioallantoic placenta(A. J. Copp, J. Embryol. Exp. Morphol., 51, 109 (1979)). This modelpresents ExE as a potential source of stem cells for the trophoblastlineage (J. Rossant and W. Tamura-Lis, J. Embryol. Exp. Morphol., 62,217 (1981)). In humans, research suggests that hTS cells may occur inthe later stages of placental development rather than in the blastocyst(J. Rossant, Stem Cells 19, 477 (2001)). Another study suggests that nohTS cells exist, and that any possible existence of hTS cells wouldlikely originate from the cytotrophoblast layer (T. Kunath et al., in:Trophoblast stem cells, chapter 12, in: Stem Cell Biology, D. R.Msrshak, R. L. Gardner, D. Gottlieb, Eds. (Cold Spring Harbor LaboratoryPress, Cold Spring Harbor, N.Y. 2001), pp. 267-287).

Other possible disadvantages of the existing cell lines are as follows:

1. Use of feeder cells for culturing the human embryonic stem cell(hESC) lines produces mixed cell population that require the embryonicstem cells (ESC) to be separated from feeder cell components and thisimpairs scale up.

2. ESC get contaminated by transcripts from feeder cells and cannot beused on a commercial scale. It can be used only for research purposes.

U.S. Appl. No. 2003104616 disclosures that Geron established a procedurewhere hESC line was cultured in the absence of feeder cells (XU et. al2001). The hESC were cultured on an extracellular matrix in aconditioned medium and expanded in this growth environment in anundifferentiated state. The hESC contained no xenogenic components ofcancerous origin from other cells in the culture. Also, the productionof hESC cells and their derivatives were more suited for commercialproduction. In this process, there was no need to produce feeder cellson an ongoing basis to support the culture, and the passaging of cellscould be done mechanically. However, the main disadvantage of thisprocedure is that the inner cell mass (ICM) is isolated by immunosurgerymethod, wherein the initial derivation of ESC is carried out usingfeeder layer containing xenogenic components. This raises the issue ofpossible contamination with animal origin viruses and bacteria.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a method for isolating theectopic pregnant mass-derived human villous trophoblast stem cell,comprising the steps of: (a) obtaining trophoblastic villi from a tubalectopic pregnant mass; (b) collecting cells from the trophoblasticvilli; and (c) culturing the collected cells in a culture medium toobtain the isolated human villous trophoblast stem cell. The subjectmethod may further comprise cutting the trophoblastic villi into piecesand treating the trophoblastic villi with an enzyme.

In some embodiments, the ectopic pregnant mass-derived human villoustrophoblast stem cell expresses embryonic stem cell antigens SSEA-1,SSEA-3 and SSEA-4. The ectopic pregnant mass-derived human villoustrophoblast stem cell may also express genetic markers Octamer-4 (Oct4), trophoblast-specific receptor (FGFR2), and fibroblast growth factor4 (FGF4). In some embodiments, the ectopic pregnant mass-derived humanvillous trophoblast stem cell is capable of forming embryonic bodieswith an adhesive characteristic. The ectopic pregnant mass-derived humanvillous trophoblast stem cell is also capable of maintaining the lengthof chromosomal telomeres in passages in culture. In some embodiments,the ectopic pregnant mass-derived human villous trophoblast stem cell iscapable of differentiating into a mesenchymal cell expressing cellsurface markers CD44 and CD90. In some embodiments, the ectopic pregnantmass-derived human villous trophoblast stem cell is capable ofdifferentiating into an endodermal, mesodermal, and/or ectodermal cell.The ectopic pregnant mass-derived human villous trophoblast stem cellcan be one selected from the group consisting of osteoblast,chondrocyte, myocyte, adipocyte, neural cell, pancreatic islet stem celland progenitor cell. In some embodiments, the ectopic pregnantmass-derived human villous trophoblast stem cell has a gene-switchingmechanism that is bFGF-dependent. A mutation can be introduced into theectopic pregnant mass-derived human villous trophoblast stem cell sothat the cell is genetically modified. In some embodiments, the ectopicpregnant mass-derived human villous trophoblast stem cell produces agrowth factor or a hormone. One example of the hormone is humanchorionic gonadotropin (hCG). In some embodiments, the pregnant mass isobtained in an unruptured manner. In some embodiments, the pregnant massis at a gestational age of no older than 7 or 8 weeks. In someembodiments, the trophoblastic villi are obtained through a surgicalprocedure. In practicing the subject method, the culture medium can befree of a feeder layer. The method of the present invention can furthercomprise the steps of: (a) forming embryonic bodies (EBs) in the culturemedium; (b) treating the EBs with an enzyme; and (c) collecting cellsfrom the enzyme-treated EBs to obtain the isolated human villoustrophoblast stem cell. Also provided by the present invention is anisolated human villous trophoblast stem cell prepared by the methoddescribed herein.

In another aspect, the present invention provides a method for treatingor preventing a disease or a condition comprising administering to asubject in need thereof an effective amount of an isolated human villoustrophoblast stem cell prepared using the subject method disclosedherein. In some embodiments, the disease is an immunodeficient disease,a nervous system disease, a hemopoietic disease, a cancer, or diabetes.The cancer can be a carcinoma. Examples of the cancer include anadenocarcinoma or choriocarcinoma. The choriocarcinoma can be syncytiomamalignum. In some embodiments, the nervous system disease is aneurodegenerative disease. The neurodegenerative disease can beParkinson's disease, Huntington's disease, Alzheimer's disease,amyotrophic lateral sclerosis (ALS), multiple system atrophy, Lewy bodydementia, peripheral sensory neuropathy, spinal cord injury, or achemical induced neuron damage. In some embodiments, theneurodegenerative disease is Parkinson's disease. The neurodegenerativedisease may result in a loss or damage of dopaminergic neurons. In someembodiments, the human villous trophoblast stem cell differentiates intoneuron in situ. In some embodiments, the human villous trophoblast stemcell differentiates into dopaminergic neuron in situ. In someembodiments, the human villous trophoblast stem cell, uponadministration to the subject, migrates to substantia nigra parscompacta (SNc) region of the brain of the subject. In some embodiments,the condition is habitual abortion or implantation IVF failure. Thesubject method for treating or preventing a disease or a condition usingthe isolated human villous trophoblast stem cells may further compriseadministering to the subject an effective amount of a therapeuticcompound. The therapeutic compound can be a drug, a chemical, or anantibody. In some embodiments, the method further comprisesadministering to the subject an effective amount of a compound thatmodulates bFGF, Oct 4, FGFR-2 or FGF4. The compound can be an inhibitorof bFGF, Oct 4, FGFR-2 or FGF4. In some embodiments, the subject is amammal, preferably a human. The administering of the cells can be viainjection, transplantation, or surgical operation. In some embodiments,the administering of the human villous trophoblast stem cell isperformed into the striatum region of the brain of the subject.

In yet another aspect, the present invention provides a method forscreening for therapeutics that modulate human villous trophoblast stemcell differentiation or activity comprising: (a) subjecting an isolatedhuman villous trophoblast stem cell prepared using the method of claim 1to a test substance; and (b) evaluating the effect of the test substanceto determine if the test substance modulates human villous trophoblaststem cell differentiation or activity.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C show display of hTS cells in early mesenchymal villi andterm placenta. (1A) tEBs formed from dispersed trophoblastic cellsculture. (1B) expressions of SSEAs and Thy-1 in the tEBs derived cellsby flow cytometry. Immunocytochemically, SSEA-1 expressed in thecytoplasm (1C) while SSEA-3 in the nucleus (1D) and SSEA-4 in the cellmembrane (1E). Immunohistochemically, in the early cytotrophoblasts,SSEA-1 appeared mainly in the cell membrane and few in the cytoplasm(1F), SSEA-3 in the nucleus (1G), and SSEA-4 in the cell membrane (1H).At term villi, detectable SSEA-1 (1I), SSEA-3 (1J), and SSEA-4 (1K)shown in the mature intermediate villous stroma. SSEA-1 stained cells inthe vein of fallopian tissue (1L) and umbilical cord veins (1M). SSEA-3(1N) and SSEA-4 (1O) stained cells in the umbilical cord veins.

FIGS. 2A-2I show in vitro differentiations of hTS cells into specificcell phenotypes of all three germ layers. (2A) tEBs derived mesenchymalstem cells by flow cytometry. CD 44 and CD 90 for mesenchymal stem cells(upper), CD 34 and CD 45 for hematopoietic stem cells (lower).Osteogenic differentiation identified with: Alizarin red S (2B), vonKossa (2C), and alkaline phosphatase activity stains (2D); Alician bluefor chondrogenesis (2E); Myosin heavy chain stain for skeletal muscle(2F); and Oil red O for adipogenesis (2G). (2H) Neural stem cells:neurofilament (left), nestin (middle), and GFAP (right) measured by flowcytometry (upper). The peak responsiveness for neurofilament and GFAPwas at 10th day of induction, while that of nestin was less (lower).(2I) Gene expressions by RT-PCR analyses: osteopontin and osteocalcinfor osteoblasts; perlecan and collagen type II for chondrocytes;myogenin and myoD1 for myocytes; PPAR.gamma.-2 and adipsin foradipocytes; and PDX-1 for pancreatic islet beta-cells. Positiveexpressions appeared 7 days after induction.

FIGS. 3A-3D show in vivo characteristics and functionality of hTS cells.(3A) hTS cell-induced chimeric reactions in SCID mice; (upper) needletract (NT) and (lower) bizarre cells (black arrow) between the musclefibers (blank arrow). (3B) Karyotype of the hTS cells with 46 normalchromosomes (XY). (3C) Telomere length of hTS cells at passage 3 (8.0kb) and passage 7 (7.8 kb). (3D) Functionality of hTS cells analyzed byRT-PCR. In lane 1, primary cultured hTS cells expressed Oct4, fgfr-2,and FGF4, and in lane 2 Oct4 and fgfr-2 were down regulated by addingbFGF (10 ng/ml) in hTS cells (passage 6). In lane 3 no bFGF was to hTScells (passage 6). In lane 4 only fgfr-2 was expressed in the termplacental cells. p2-microglobulin as cDNA positive control.

FIGS. 4A-4K show functional assessments of hTS cell-derived neural stemcells. (4A) Expression of F1B-FGP transfected hTS cells (green color).(4B) Expression of TH-2-FITC (green color) in induced neural stem cells.(4C) Expression of F1B-FGP in induced neural stem cells (green color).(4D) Expression of TH-16-PE (red color) in F1B-FGP transfected hTScells. (4E) Co-expressions of TH-16-PE (red color) and F1B-FGPtransfected (green color) in induced neural stem cells. A unilateral(right) 6-OHDA-lesion model of Parkinson's disease is performed in rats.Immunohistochemical asssays after 6-OHDA-lesions showed no THimmunoreactivities were detected in the lesioned areas of striatum (str,upper, f), subthalamic nucleus (stn, lower, g), and substantia nigracompacta (snc, lower, not shown) in comparison with the positiveresponses (dark brown) in control areas. (4F) Treated with PBS as groupc (gr. c). (4G) Treated with induced hTS cell-FGP transfected as group b(gr. b). (4H) Treated with non-induced hTS cell-FGP transfected as groupa (gr. a) showed positive TH immunoreactivities in the previouslylesioned striatum (upper, right) and substantia nigra compacta (lower,right). Immunofluorescent observation found several clusters ofFGP-transfected hTS cells (green) scattered in the previously lesionedstriatum (4I) and a cluster of FGP-transfected hTS cells and somescattered cells (green) in the substantia nigra compacta (4J). Arrowindicates needle tract. (4K) Apomorphine-induced rotation tests after6-OHDA-lesioned hemiparkinsonian rats treated with induced andFGP-transfected hTS cells (gr. b, closed triangle) and treated withnon-induced but FGP-transfected hTS cells (gr. a, closed circle).Control group was injected with PBS (gr. c). Significance (*: p<0.05)tested by LSD post hoc comparisons after repeated-measure ANOVA, p=0.037(a vs. c) and p=0.008 (b vs. c) at 6 weeks; p=0.019 (a vs. c) at 9weeks; p=0.005 (a vs. c) and p=0.018 (a vs. b) at 12 weeks.

FIGS. 5A-5H show morphological differentiation and de-differentiation ofhTS cells during drug induction into pancreatic islet-like cells. (5A)Appearance in fibroblastic cells before induction. (5B) Pre-inductionwith LDMEM-mn at 6 h with multicystic features and (5C) after 24 h withgrape-like cluster formation. (5D) HDMEM-mn induction at 6 h with moreapparent grape-like cell clusters. Fibroblastic outgrowths from the cellcluster appeared at 18 h (5E), 48 h (5F) and 96 h (5G) after cultured inbasic medium showing morphological de-differentiation. (5H) Peakimmunoreactive insulin secretion from differentiated hTS cells intoculture medium appeared after HDMEM-mn induction for 6 h.

FIG. 6 shows insulin-related neuroendocrine components innon-drug-induced and drug-induced hTS cells shown in RT-PCR. Theleft-side of each column indicates pre-induced and right-side of eachcolumn indicates induction at 30 h.

FIGS. 7A-7F show immunocytochemistry of insulin-related proteins indifferentiated hTS cells. Positive immunocytochemical reactions weredetected in cells with (7A) insulin, (7B) insulin-like growth factor-1(IGF-1), (7C) glucagons, (7D) amylase, (7E) tau and (7F) MAP-2.

FIG. 8 shows glucose equilibrium in the Transwell dish with hTS cellsimplantation. (top) indicating the drug-induced hTS cells and (middle)indicating non-drug-induced control. (bottom) arrow indicates a 7 mm 3-Dcellular mass on the collagen matrix.

FIGS. 9A-9F show immunoreactive insulin in tissue derived fromdrug-induced hTS cells. Around 10 cell layers proliferated from both(9A) non-drug-induced hTS cells as control and (9B) drug-induced hTScells as study by hematoxylin eosin stain. Negative immunoreactiveinsulin expression in control (9C) but positive detection in study (9D).Positive control of insulin staining is preformed in islet of normalpancreas (9E) and cells of insulinoma (9F).

FIGS. 10A-10C show ectopic tubal pregnancy mass at 7 weeks of gestationlaparoscopically (10A, left) and the trophoblastic villi are dissectedfor further preparation and establishment of cell line (10A, right).(10B) and (10C) show immunohistochemical examinations of SSEAsexpression on trophoblastic villi and fallopian tissues. (10B) SSEA-1expressed cells are seen in the loose stromal mesoderm (black arrowhead), capillary wall (white arrow), and capillary intrlumen (whitearrow head). SSEA-3 and SSEA-4 were negative staining (10C) SSEA-1expressed cells (brown stained) appeared in a vessel of fallopiantissue.

DETAILED DESCRIPTION OF THE INVENTION Term Definition:

Gene therapy: the use of genes and the techniques of genetic engineeringin the treatment of a genetic disorder or chronic disease. There aremany techniques of gene therapy, all of them still in experimentalstages. The two basic methods are called in vivo and ex vivo genetherapy. The in vivo method inserts genetically altered genes directlyinto the patient; the ex vivo method removes tissue from the patient,extracts the cells in question, and genetically alters them beforereturning them to the patient.

Immunodeficient disease: in medicine, immunodeficiency (or immunedeficiency) is a state in which the immune system's ability to fightinfectious disease is compromised or entirely absent. Most cases ofimmunodeficiency are either congenital or acquired.

Nervous system disease: refers to any condition characterized by theprogressive loss of neurons, due to cell death, in the central nervoussystem of a subject.

Tumor: The tumor include abnormal cancer cells associated with lymphoma,leukemia, plasma cell dyscrasias, multiple myeloma, amylodosis, also asknown as hematopoietic tumors, colorectal cancer, ovarian cancer, bonecancer, renal cancer, breast cancer, gastric cancer, pancreatic cancer,or melanoma.

This invention provides an isolated preparation of human trophoblaststem cells which is obtained from embryo at fallopian tube of ectopicpregnancy. The human trophoblast stem cell (hTS) is capable ofindefinite proliferation in vitro in an undifferentiated state. The hTScell maintains the potential multilineage differentiation capabilities.The hTS cell preparation can be induced to differentiate into cells ofthe trophoblast lineage in vitro or in vivo. The invention thereforealso relates to a purified trophoblast stem cell preparation of theinvention (preferably cultured in vitro) induced to differentiate intocells of the trophoblast lineage. This differentiated cell preparationis characterized by expression of genetic markers of trophoblast celllineages (e.g. diploid trophoblast cells of the ectoplacental cone(EPC), and the secondary giant cells of the early conceptus). In anembodiment, the purified trophoblast cell isolation comprises cells ofthe trophoblast lineage including diploid trophoblast cells.

The isolated cells are positive for the SSEA-1 marker, positive for theSSEA-3 marker, and positive for the SSEA-4 marker, are pluripotent andhave karyotypes and in which none of the chromosome are altered. In anembodiment, the cells are characterized by expression of the geneticmarkers Oct 4, fgfr-2, and FGF4.

The isolated hTS cell has normal karyotypes after subsequent cultures invitro, which maintains length of telomere which does not become shorterafter subsequent cultures in vitro.

In the preferred embodiment, the hTS cells are positive for cell surfacemarkers CD44 and CD90. Further, the hTS cells can be induced fordifferentiating into several kinds of cells. In the preferredembodiment, the cells differentiate into endodermal, mesodermal, and/orectodermal derivatives. In more preferred embodiment, the derivative isosteoblast, chondrocyte, myocyte, adipocyte, and/or neural stem cell.For differentiating into different functional cell types, the cells havegene switch. In the preferred embodiment, the gene switch is induced bybFGF.

The hTS is provided for use in model of human cell differentiation, genetherapy, or cell-based therapy.

The isolated hTS cell can be modified by introducing mutations intogenes in the cells or by introducing transgenes into the cells.Insertion or deletion mutations may be introduced in a cell usingstandard techniques. A transgene may be introduced into cells viaconventional techniques such as calcium phosphate or calcium chlorideco-precipitation, DEAE-dextran-mediated transfection, lipofection,electroporation, or microinjection. Suitable methods for transformingand transfecting cells can be found in Sambrook et al. (MolecularCloning: A Laboratory Manual, 2nd Edition, Cold Spring Harbor Laboratorypress (1989)), and other laboratory textbooks. By way of example, atransgene may be introduced into cells using an appropriate expressionvector including but not limited to cosmids, plasmids, or modifiedviruses (e.g. replication defective retroviruses, adenoviruses andadeno-associated viruses). Transfection is easily and efficientlyobtained using standard methods including culturing the cells on amonolayer of virus-producing cells.

The hTS cell preparations of the invention can be used to produce growthfactors, hormones, etc. relevant to human placenta. The cellpreparations or cell lines of the invention can also be used to producetherapeutics such as human Chorionic Gonadotropin (hCG).

The hTS cell preparations of the invention can be used to screen forgenes expressed in or essential for trophoblast differentiation.Screening methods that can be used include Representational DifferenceAnalysis (RDA) or gene trapping with for example SA-lacZ. Gene trappingcan be used to induce dominant mutations (e.g. by deleting particulardomains of the gene product) that affect differentiation or activity oftrophoblast cells and allow the identification of genes expressed in oressential for trophoblast differentiation.

This invention also provides a method for obtaining human stem cellscomprising (a) obtaining embryo at fallopian tube of ectopic pregnancy;and (b) obtaining the stem cells from the villous trophoblast of theembryo; wherein the human stem cells are human trophoblast stem cells asdescribed above. The embryo is obtained from the unruptured ectopicpregnancy. In a preferred embodiment, the unruptured ectopic pregnancyis in the stage less than 6 weeks postfertilization. The villoustrophoblast comprises cytotrophoblastic layer.

This invention also provides a combination for therapy comprising (a) anisolated preparation of human trophoblast stem cells and (b) a buffersolution, wherein the human stem cells are human trophoblast stem cellsas described above. The buffer solution of the combination is providedfor maintaining biological activities of the stem cells. For example butnot limiting, the buffer solution is saline, PBS, and medium.

The combination further comprises a therapeutic compound. For examplebut not limiting, the therapeutic compound is drug, chemical, andantibody. In an embodiment, the therapeutic compound isimmunosuppressive agent or supportive agents.

The combination of this invention is provided for therapy of diseasescomprising immunodeficient diseases, nervous system diseases,hemopoietic system diseases, or tumors. The combination of thisinvention is used in transplantation, injection, or externalapplication.

This invention further provides a method for monitoring the status ofcontraception comprising assaying bFGF, Oct4, fgfr-2, and/or FGF4 levelsin the endometrium, wherein the status of contraception is directed toimplantation and placentation.

This invention further provides a composition for use in the treatmentof patients suffering from habitual abortion and/or IVF failurecomprising monocloned antibodies, antagonists and other inhibitors toregulate bFGF, Oct4, fgfr-2, and FGF4 levels, wherein the treatmentinvolves Oct4 and fgfr-2 expressions knockdown by bFGF. The IVF failureis frequent IVF failure.

This invention further provides a method for use in treating orpreventing cancer comprising administering to an animal in need thereofan effective amount of monocloned antibodies, antagonists and otherinhibitors to regulate bFGF, Oct4, fgfr-2, and FGF4 levels. In anembodiment, the animal is mammalian. In a preferred embodiment, theanimal is human.

The method of this invention can be used in treating or preventingcancer, wherein the cancer is carcinoma. Further, the carcinoma isadenocarcinoma or choriocarcinoma. In a preferred embodiment, thechoriocarcinoma is syncytioma malignum.

This invention further provides a composition for treating a nervoussystem disease comprising human trophoblast stem cells, wherein thehuman trophoblast stem cells are obtained from embryo of ectopicpregnancy. The nervous system disease is neurodegenerative disease.Neurodegenerative disease refers to any condition characterized by theprogressive loss of neurons, due to cell death, in the central nervoussystem of a subject. In the preferred embodiment, the neurodegenerativedisease is Parkinson's disease, Huntington's disease, Alzheimer'sdisease, amyotrophic lateral sclerosis (ALS), multiple system atrophy,Lewy body dementia, peripheral sensory neuropathies or spinal cordinjuries. In the more preferred embodiment, the diseaseneurodegenerative disease is Parkinson's disease.

The composition of this invention further comprises a buffer solution,which is provided to maintain the bioactivities of the human trophoblaststem cell. For example but not limiting, the buffer solution is saline,PBS, and medium.

The composition of this invention further comprises a therapeuticcompound. For example but not limiting, the therapeutic compound isdrug, chemical, and antibody.

This invention further provides a method for treating aneurodegenerative disease comprising administering a patient with aneffective amount of trophoblast stem cells. The trophoblast stem cell isobtained from trophoblastic villi at fallopian tube of ectopicpregnancy. In the preferred embodiment, the neurodegenerative disease isParkinson's disease, Huntington's disease, Alzheimer's disease orchemical-induced neuron damage.

The administering is via injection, transplantation or surgicaloperation.

In the embodiment, the patient is animal. In the preferred embodiment,the animal is human.

This invention also provides a composition for treating diabetescomprising human trophoblast stem cell as described above. Thecomposition further comprises a pharmaceutical acceptable carrier,wherein the carrier is for maintaining bioactivities of the stem cell.For example but not limiting, the carrier is saline, PBS, and medium.

The composition of this invention can be administered by injection,transplantation or surgical operation. The concentration or amount ofthe composition can be well judged by the person skilled in the art.

EXAMPLE

The examples below are non-limiting and are merely representative ofvarious aspects and features of the present invention.

Example 1 Primary Culture and Isolation of hTS Cells from TrophoblasticVilli

Using a laparoscopy, eight eligible samples (4-5 weekspost-fertilization) were obtained from the gynecologic unit (FIG. 10 a).The samples were used for cell culture and for immunohistochemicalstudy. Fresh villi (FIG. 10 b) were mechanically dissected, washed, andcultured with medium in the absence of bFGF. Prior to differentiation,only few EBs appeared on day one of the culture (FIG. 1 a). After aweek, EBs count increased to 30-40 in number with identicalmorphological features described in previous studies (M. Amit et al.,Dev. Biol., 227, 271, (2000); M. J. Shambloott et al., Proc. Natl. Acad.Sci. USA., 98, 113, (2001)).

Early trophoblastic villi were obtained from the unruptured tubalectopic pregnant mass (gestational age: 6-7 weeks) (FIG. 10 a) underlaparoscopic surgery. Immediately, villous tissues were washed by normalsaline (37° C.) to get rid of blood and dissected in serum free a-MEMmedium (minimum essential medium modification a-MEM, Sigma-Aldrich, St.Louis, Mo.) microscopically to avoid contamination with embryoniccompartment. Villi were cut into very small pieces and transferred to a15 ml conical tube for 3 min at room temperature (FIG. 10 b and c). Thesupernatant was removed for centrifugation at 1500 rpm for 6 min. Aftercentrifugation, the pellets were digested with 0.025% trypsin/EDTA(Sigma-Aldrich) in final dilution at 37° C. for 40 min. Digestion wasstopped by adding α-MEM containing 10% fetal bovine serum and washedagain. The pellets were re-suspended with 8 ml α-MEM containing 20% FBS(HyClone, Logan, Utah) and 1% penicillin/streptomycin, seeded onto two10 cm culture dishes and incubated in 5% CO₂ at 37° C.

Embryonic bodies (EBs) formed after day 2 of culture. The EBs mightincrease to 30-40 in number after one week of culture. These EBs werecollected, trypsinized as before and cultured again. By 7-10 days, amonolayer of fibroblast-like cells formed. They were trypsinized andwashed twice by PBS. The cells were collected for storage in liquidnitrogen by adding 10% DMSO/FBS (Sigma-Aldrich).

In the culture, the EBs appeared to adhere to the dish, as opposed tothose derived from hEG cells, which tend to float in a suspended state(B. Gerami-Naini et al., Endocrinology, 145, 1517 (2004); L. Cheng, H.Hammond, Z. Ye, X. Zhan, G. Dravid, Stem Cells, 21, 131 (2003)). Whatcaused this difference remains unclear. We suggest that the adhesivenessmight be related to the implantation characteristics of trophoblast. TheEBs were then trypsinized and cultured again. The harvested cells wereeither moved immediately to the study or stored with liquid nitrogen andlater thawed before use.

For cell culture, the cells were thawed and re-cultured in conditioneda-MEM medium containing 20% FBS, 1% penicillin-streptomycin and with 10ng/ml bFGF (CytoLab Ltd, Rehovot, Israel) or without bFGF at 37° C. with5% CO₂. Medium was changed after 3 days of culture. Half the medium waschanged every 3 days thereafter. Cells were passaged by trypsinizationupon reaching 90-95% confluence of the dish. After 5 passages,differentiations into a variety of specific cell phenotypes wereperformed to ensure the capability for multilineage pluripotency. hCG inculture medium were determined by a specific radioimmunoassay kit(Diagnostic Products, Los Angeles, Calif.).

Example 2 Immunocytochemical Study of Differentiated hTS Cells

At passage 6, cells were cultured as a monolayer in basal medium (a-MEMcontaining 20% FBS and 10 ng/ml bFGF) in 3.5 cm culture dishes. Aftercells grew to 70% in confluence, culture medium was changed for variabledifferentiations. The evaluations were made at day 7, 14, 21, and 28after drug induction. For osteogenic differentiation, cells were grownin conditioned medium (Table 1).

TABLE 1 Recipes used for specific cell phenotype differentiations of hTScells Table 1. Recipes used for specific cell phenotype differentiationsof hTS cells Differentiations Reagents Osteogenesis α-MEM containing 20%FBS, 10 μg/ml bFGF, 0.1 μM dexamethasone, 10 mMβ-glycerolphosphate, and0.2 mM ascorbic acid Chondrogenesis α-MEM containing 10% FBS, 1%antibiotic/antimycotic, 6.25 μg/ml insulin, 10 ng/ml TGE-β1, and 50 nMascorbate-2-phosphate Myogenesis α-MEM containing 10% FBS, 10 μg/mlbFGF, 0.1 mM dexamethasone, 50 mM hydrocortisone, and 5% horse serumAdipogenesis α-MEM containing 20% FBS, 10 μg/ml bFGF, 10 μg/ml insulin,1 μM dexamethasone, 0.5 mM isobutyl methylxanthine, and 200 μMindomethacin. Neurogenesis α-MEM containing 20% FBS and 10 μM alltrans-retinoic acid Pancreaticislet beta- L-DMEM containing 20% FBS, 5.5mmol/L glucose, 10 mmol/L cells nicotinamide, 1 mmol/Lβ-mercaptoethanol, H-DMEM containing 15 mmol/L glucose, 10 mmol/Lnicotinamide, 1 mmol/L β-mercaptoethanol HBS solution NaCl: 867 g in 80ml Milli Q, 2 ml 1M HEPES (GIBCO HEPES Buffer solution cat. No.:15630-080), adjusted pH to 7.4 and filted by 0.2 μm filter and stored at4° C.

Medium changes were performed twice weekly, with a medium volume of 2 mlper dish. The cells were subjected to immunocytochemical stains. (A)Cytochemical mineral matrix was analyzed by Alizarin red S (AR-S) assayto identify its calcium mineral content (S1). Cells were rinsed with PBSfollowed by fixation in ice-cold 70% ethanol for 1 h and rinsed withde-ionized water followed by 40 mM AR-S (pH 4) at room temperature for10 min. The cells were then rinsed five times with water and then washedwith PBS for 15 min to reduce non-specific AR-S stain. (B) For von Kossastain (S2), cell layers were fixed with 10% formaldehyde for 1 h,incubated with a 2% silver nitrate solution (w/v) for 10 min in thedark, washed thoroughly with de-ionized water, and then exposed tobright light for 15 min. (C) Alkaline phosphatase activity was measuredusing a commercial kit (Sigma-Aldrich) (S3). (D) Chondrogenicdifferentiation (S4) was induced with a conditioned medium (Table 1).Chondrogenesis was confirmed by Alcian blue (Sigma-Aldrich) staining atan acidic pH. Cells were fixed with 4% formaldehyde for 15 min at roomtemperature and washed with PBS several times, then incubated for 30 minwith 1% Alcian blue in 0.1 N HC1 (pH 1.0) and finally, washed with 0.1 NHCl for 5 min to remove excess stain. (E) Myogenic differentiation (S4)was induced in conditioned medium (Table 1) for 4 weeks and confirmed byimmunocytochemical staining for the myosin heavy chain. Cells wererinsed twice with PBS, fixed for 20 min with 4% formaldehyde, and washedseveral times with PBS. The cells were then incubated with 3% hydrogenperoxide in PBS for 10 min to quench endogenous peroxidase enzymeactivity, and non-specific sites were blocked by incubation in blockingbuffer (PBS containing 10% HS, 0.1% Triton X-100) for an additional 60min. The cells were washed three times for 5 min each in blocking bufferand incubated for 1 h in blocking buffer containing skeletal musclemyosin heavy chain specific monoclonal antibody (Vector Laboratories).The cells were washed in blocking buffer and detected using theVectaStain ABC kit (Vector Laboratories). (F) Adipogenic differentiation(S5) was induced in conditioned medium (Table 1). Cells were fixed for60 min at room temperature in 4% formaldehyde/1% calcium and washed with70% ethanol. They were incubated in 2% oil red O reagent for 5 min atroom temperature. Excess stain was removed by washing with 70% ethanolfollowed by several changes of distilled water. The assay was using anoil red O stain as an indicator of intracellular lipid accumulation.

Immunohistochemically, detection of the SSEA-1 (Chemicon, D3P013A),SSEA-3 (Chemicon, 24040550), and SSEA-4 (Chemicon, 24080406) expressionswas performed using LSAB kit (Dako, k0697) and Double AB (Dako, k3466).Goat serum (Dako, x0907) was used as a blocking antigen. The stainingprocedures of SSEA-1 and SSEA-4 on the de-paraffined tissue sectionswere as follows: 1) rinsing with tris-phosphate buffer saline (TBS); 2)cleaning by H₂O₂ for 10 min; 3) blocking with goat serum for 30 min; 4)adding primary antibody and incubated for overnight; 5) rinsing withTBS; 6) treated with streptavidin for 20 min; 6) rinsing with TBS; 7)stained by biotin (20 min); 8) washing with TBS 9) treated with DAB (10min) and counterstained with Mayer hematoxylin. For SSEA-3 staining,similar procedures were done. An additional step: retrive antigen byhigh pressure cooker in citrate buffer for 15 min, was added betweenstep 1 and 2. As a result, expressions of SSEA-1, SSEA-3, and SSEA-4appeared in the intracytoplasm, the nuclear membrane, and the cellmembrane, respectively. However, a small number of cultured cells showedSSEA-4 staining in both intracytoplasm and cell membrane.

First, essential surface markers were applied to detect the existence ofstem cells in the culture. After the first passage, cells were fixed inneutralized 4% formaldehyde and subjected to immunocytochemical testsfor the essential surface markers of stem cell; stage-specific embryonicantigens, SSEA-1, SSEA-3, and SSEA-4. The results positively indicatedthe existence of pluripotent stem cells. Some giant cells displayedSSEA-1 in the cytoplasm of cells (FIG. 1 c). SSEA-3 appeared in thenuclear membrane (FIG. 1 d), while SSEA-4 appeared in both the cytoplasmand cell membrane (FIG. 1 e). The cell was large and round in shape witha 1:1 nucleus to cytoplasm ratio.

The SSEA expressions immunohistochemically were further confirmed byexamining the locations of these SSEAs in the ectopic villous tissues.In the villi, all SSEA stained cells were localized at the Langhanslayer (inner layer), where SSEA-1 expressions appeared in the cytoplasmof cells (FIG. 1 f). SSEA-1 stained cells were also found in the loosemesodermal stroma, the endothelium of capillary, and the intraluminalspace (FIG. 10 b). SSEA-1 stained cells could also be seen in the lumenof vessels of the fallopian tissues (FIG. 10 c). SSEA-3 and SSEA-4appeared in the nuclear membrane and cell membrane, respectively (FIG. 1g and h) (Table 1).

With SSEA expressions in the Langhans layer, it was proceed withimmunostaining of human chorionic gonadotropins (hCG), an indication ofthe existence of trophoblastic cells. This invention resulted with hCGexpression only in the syncytiotrophoblasts (outer layer) but not in theLanghans layer. The lack of hCG expression in the Langhans layersuggests that hTS cells are distinct from syncytiotrophoblast cells. Tofurther support these findings, it was measured SSEA-1, SSEA-3, SSEA-4,and Thy-1 expressions using various antibodies by flow cytometry. Inthree cell lines (PV 02, PV 06, and PV 07), the cells that expressedwith SSEA-1, SSEA-3, SSEA-4, and Thy-1 occupied 6.8±1.5%, 43.2±4.9%,53.2±0.8%, and 94.3±1.8% of 10,000 cell counts, respectively (FIG. 1 b).It was observed that SSEA-4 expression appeared in both the cytoplasmand the cell membrane immunocytochemically, but it appeared only in thecell membrane immunohistochemically. This result possibly reflects thedifferent developmental status of the cytoplasm and the cell membrane ofthe cells.

In term placentae, cells stained with SSEAs were not found in theterminal villi, but in the intravillous stroma of larger stem villi(FIGS. 1 i, j). SSEA-3 was distributed in the syncytial sprouts as well(FIG. 1 k). Together, these findings provide evidence that in the earlymesenchymal hTS cells are located at a histological site identical tothat of cytotrophoblasts and express all SSEAs surface markers.

Because SSEA-1 stained cells were observed in the venous vessels of thetubal tissues in ectopic gestation (FIG. 11), the relationship betweenumbilical cord blood-derived mesenchymal stem cells and the hTS cellshad to be clarified. To do this, it was investigated whether theSSEAs-stained cells appeared in blood vessels of term placentae locatednear the placenta-umbilical cord junction. An abundance of SSEA-1—(FIG.1 m), SSEA-3—(FIG. 1 n), and SSEA-4—stained cells (FIG. 1 o) wereobserved in the umbilical veins, but not in the artery.

These results prompted to ask whether those cells possess pluripotentcapability in differentiation into a variety of specific cell phenotypesas hES/hEG cells do. The cells were cultured in different conditionedα-MEM media according to the differentiation induction. hCG was measuredusing radioimmunoassay and became undetectable after passage 1 (PV 07cell line) and passage 2 (PV 02 cell line) in the culture medium. After6 passages, differentiations of specific cell phenotypes includingosteoblasts, chondrocytes, adipocytes, myocytes, and neural cells wereinitiated by a variety of drug inductions (Table 1). Immunocytochemicalevaluations were made on day 7, 14, 21, and 28 after induction (12).

The results demonstrated positive stains with Alizarin red S, von Kossa,and alkaline phosphatase for osteoblasts (FIG. 2 b, c and d), Alicianblue for chondrocytes (FIG. 2 e), myosin heavy chain for myocytes (FIG.2 f), and oil red O and intracellular lipid formation for adipocytes(FIG. 2 g). This illustrated that the cells possess mesenchymalpluripotency for differentiation to specialized cell phenotypes,depending on the drugs administered.

Example 3 RT-PCR

Extraction of total RNA from the hTS cells (10⁵ to 10⁶) at variouspassages of culture and term placental tissues was carried out using theTRIzol kit according to the manufacturer's instructions (Invitrogen,Carlsbad, Calif.). Reverse transcription was performed using 1 μg RTreactions were performed using Ready-to-Go, RT-PCR Beads kit (AmershamBiosciences, Buckinghamshire, UK). One .mu.g of total RNA was reversetranscribed to cDNA. The cDNA product, corresponding to 0.2 μg of totalRNA, was used for PCR amplification. The primers used were shown inTable 2.

TABLE 2 Primer sequences used for RT-PCR(SEQ ID NOs 1-26, respectively, in order of appearance)Table 2. Primer sequences used for RT-PCR Osteopontin(5′-CTAGGCATCACCTGTGCCATACC-3′ forward and5′-CAGTGACCAGTTCATCAGATTCATC-3′ reverse) Osteocalcin(5′-CGCAGCCACCGAGACACCAT-3′ forward and 5′-GGGCAAGGGCAAGGGGAAGA-3′reverse) Perlecan (PRLN) (5′-CATAGAGACCGTCACAGCAAG-3′ forward and5′-ATGAACACCACACTGACAACC-3′ reverse) Collagen type∩(5′-ACGGCGAGAAGGGAGAAGTTG-3′ forward and 5′-GGGGGTCCAGGGTTGCCATTG-3′reverse) Myogenin (5′-AGCGCCCCCTCGTGTATG-3′ forward A and5′-TGTCCCCGGCAACTTCAGC-3′ reverse) MyoD1 (5′-CGGCGGCGGAACTGCTACGAA-3′forward and 5′-GGGGCGGGGGCGGAAACTT-3′ reverse) PPARγ-2(5′-GCTGTTATGGGTGAAACTCTG-3′ forward and 5′-ATAAGGTGGAGATGCAGGCTC-3′reverse) Adipsin (5′-GGTCACCCAAGCAACAAAGT-3′ forward and5′-CCTCCTGCGTTCAAGTCATC-3′ reverse) Pdx-1 (5′-GTCCTGGAGGAGCCCAAC-3′forward and 5′-GCAGTCCTGCTCAGGCTC-3′ reverse) Oct4(5′-GGAAAGGCTTCCCCCTCAGGGAAAGG-3′ forward and5′-AAGAACATGTGTAAGCTGCGGCCC-3′ reverse) fgfr-2(5′-GGAGGGGATGTGGAGTTTGT-3′ forward and ′5′-ACTGGTTGGCCTGCCCTATA-3′reverse) FGF4 (5′-AGCGAGGCGTGGTGAGCATCTT-3′ forward and5′-TGGTCCGCCCGTTCTTACTGAG-3′ reverse) β2-microglobulin(5′-CTCGCGCTACTCTCTCTCTTTCTGG-3′ forward and5′-GCTTACATGTCTCGATCGCACTTAA-3′ reverse)

Primer used for the reaction products were applied with electrophoresisin a 1.5% agarose gel and visualized with ethidium bromide. Primer forp2-microglobulin was used as cDNA positive control to assure evenloading of the gel. For each set of PCR reaction, a control, in whichwater was added rather than cDNA, was included. Each control reactionwas uniformly negative.

With RT-PCR, various primer sequences were used to identify the geneticexpressions in the cultured cells (PV 02, passage 4). The primers usedincluded: osteopontin and osteocalcin for osteoblasts, perlecan andcollagen type II for chondrocytes, myogenin and myoD1 for myocytes,PPAR.gamma.-2 and adipsin for adipocytes (12) (Table 2). The resultsindicated that all the above genetic expressions appeared within 7 daysafter induction in the cells (FIG. 2 i). Among them, very strong geneexpression was seen in myoD1 at 7 days. Additionally, neurogenicdifferentiation of the cells (PV 02 at passage 5, PV 07 at passages 3and 4) was induced by retinoic acid and detected by flow cytometry.Expressions of neurofilament protein, GFAP, and nestin could be detectedat day 4 after induction. Expressions of neurofilament protein (thestrongest) and GFAP upregulated to day 10 then diminished. Very weakexpression of nestin was seen in the first 10 days and disappeared after14 days of induction (FIG. 2 h). These results confirmed that in anundifferentiated state, these cells possess capability fordifferentiation to mesenchymal multilineages similar to that of hES/hEGcells.

Example 4 Chromosome and Telomere Length Analyses

hTS cells were incubated with 0.1 μg/ml of colcemid for 3 hours. Aftertrypsinization, they were re-suspended in 0.075 mol/L of KC1, incubatedfor 20 minutes at 37° C., and then fixed in methanol/acetic acid at aratio of 3:1. Metaphase chromosomes were obtained from a 25 cm cultureflask of hTS, according to standard procedures, and analyzed afterG-banding (S7). Karyotype of human chromosomes was examined afterstaining by cytogenetic specialists.

Since the presence of telomerase activity does not always imply thattelomere length will be stable and static. Telomerase activity isupregulated when stem cells are stimulated to generate progenitor cells(S8). We selected to measure the telomere length to see whether thetelomere shortening occurred in hTS cells during subsequent culture(S9). Thus, genomic DNA was prepared in a 10 cm cell culture dish, grownto saturation, and digested with Hinf I and Rsa I before electrophoresison a 1% agarose gel. The fragments were transferred to Hybond N+nylonmembranes (Amersham) and hybridized at 65 degrees to a probe (TTAGGGrepeats) labeled with α-³²P-dCTP using Ready-To-Go labeling beads(Amersham Biosciences, UK). Telomere length was assessed by Southernblot analysis of terminal restriction fragments (TRFs) obtained bydigestion of genomic DNA. The TRFs obtained contain DNA with uniformtelomeric (TTAGGG) repeats as well as degenerated repeats other than atthe distal end of the chromosome sub-telomeric region. After digestion,the DNA fragments are separated by gel electrophoresis and blotted. TRFswere visualized by hybridization with labeled oligonucleotidescomplementary to the telomeric repeat sequence. Finally, the sizedistribution of the TRFs can be compared to a DNA length standard. Theresults indicated that hTS cells at passage 3 and 7 (PV 02 cell line)showed 8.0 kb and 7.8 kb, respectively. It has been reported thattelomere length might be decreased with the number of cell divisions invitro and with aging in vivo (S10, S11). Although no significant loss oftelomere length was seen in the present observation, we can not excludethe possibility that the decrease of 200 by by 4 passages in the culturewas caused by the pre-existing variability in telomere length or bycell-to-cell variation of the rates of telomere shortening. This needsfurther elucidation.

The capability of those cells in producing benign teratoma was examinedas hES cells do in vivo. Cultured cells (10⁴-10⁵) at passage 3 of PV 02cell line were prepared and injected subcutaneously into severe combinedimmunodeficient mice (n=4) at the rear thigh. Histopathologically,myxoid cell-like chimeric reactions formed after 8 to 10 weeks ofinjection (FIG. 3 a), suggesting similar characteristics to hES cellsduring embryogenesis. Meanwhile, the chromosomes of these cells (46XY)at passages 3, 10 and 15 (PV 02 cell line) were analyzed, displayingnormal and identical karyotypes (12) (FIG. 3 b). Moreover, telomerelengths were measured in the cultured cells (PV 02) at passages 3 and 7with a result of 8.0 kb and 7.8 kb, respectively (12). Since thechromosome had not become shorter, this indicates that no geneticinformation was lost in these cells during the subsequent cultures (FIG.3 c). Given these observations in karyotypes and telomere lengths, itwas believed that hTS cells are present in the early trophoblastic villiand display the same characteristics as hES/hEG cells. It was suggestedthat hTS cells may be a progenitor of human umbilical cord blood stemcells. Furthermore, both cord blood-derived mesenchymal stem cells andhTS cells contain identical characteristics in gene expressions andmultilineage differentiation capabilities. The invention hasapplications in the areas of cell culture, tissue transplantation, drugdiscovery, and gene therapy.

Next, it was aimed to identify the pluripotency of hTS cells in theculture. Oct4 is a transcription factor and a key determinant ofpluripotency. Report states that Oct4 deficient embryos can stilldevelop to the blastocyst stage, but the ICM cells are no longerpluripotent leading to apoptosis of the primordial germ cells ratherthan to differentiation into a trophectodermal lineage (J. Kehler etal., EMBO Rep., 5, 1078 (2004)). Instead, the ICM cells are restrictedto differentiation along the extraembryonic trophoblast lineage (J.Nicholas et al., Cell, 95, 379 (1998)). Other researches suggest human(B. Gerami-Naini et al., Endocrinology, 145, 1517 (2004)) and mouse (J.Rossant, Stem Cells, 19, 477 (2001)) embryonic stem cells can beswitched towards the trophoblast lineage by changing culture conditionsand altering expression levels of Oct4. This leads to an interestinghypothesis that a formula of Oct4ON=ES, Oct4 OFF=TS might play a keygenetic switch (J. Rossant, Stem Cells, 19, 477 (2001)). Moreover,treatment to blastocyst outgrowths with fibroblast growth factor 4(FGF4) can increase the number of outgrowing trophectoderm cells (N.Chai et al., Dev. Biol., 198, 105 (1998)). Several related geneexpressions including Oct4, fgfr-2, and FGF4 in the hTS cells wereinvestigated by RT-PCR. The hTS cell culture (PV 07 cell line) inpassage 6 displayed Oct4, fgfr-2, and FGF4 expressions (FIG. 3 d).However, only the fgfr-2 expression was detected in the term placentaltissues, but not Oct4 and FGF4. By adding bFGF to the hTS cells, theOct4 and fgfr-2 expressions could be knockdown, indicating theinvolvement of bFGF in the gene switch regulation for stem celldifferentiation.

Example 5 Animal Model of Pakinsonism and hTS Cells TransplantationImmunocytochemical Analyses for TH Assays:

Paraformaldehyde (4%) fixed cells incubated in 0.1M PBS at 4° C.overnight after washing with PBS. After incubation with blockingsolution (50 ml 0.1 M PBS, 0.05 g sodium azide, 1% horse serum, and 10%Triton X-100) for 1 h at room temperature, the cells were washed again.Cells were added with primary antibody (Sigma): TH-2 (1:200 dilution) orTH-16 (1:200 dilution) for 2 h and washed with PBS. After incubationwith anti-mouse IgG with FITC or PE (Sigma) for 1 h, cells werethoroughly washed with PBS and subjected to immunofluorescence assay.

Transfection of hTS Cells Using F1B-GFP Reporter Plasmid:

F1B-GFP reporter plasmid was supplied by Dr. Chiu, I. M. Briefly,cultured hTS cells were co-transfected in a DNA mixture of F1B-GFP andpSV2neo (10:1 ratio, 50 μl in total). This DNA mixture was added slowlyinto 100 μl DOTAP solution containing 30 μl DOTAP Liposomal transfectionreagent (Roche Applied Science, Indianapolis, Ind.) and 70 μl HBS(Gibco, 867 g NaCl in 80 ml Milli Q water+2 ml 1M HEPES solution, pH7.4, at 4° C.) for 15 min at room temperature. The hTS cells, washed byPBS, were mixed well with the DNA mixture. After 24 h incubation, thestable cells lines were obtained by selection with G418 (400 μg/m1)(Roche Applied Science) through culture for 2-3 weeks until the colonieswere formed. The G418-resistant cells were pooled and lysed. The celllysates were analyzed by Western blotting using monoclonal anti-GFPantibody (Stratagene, La Jolla, Calif.) to quantitate the percentage oftransfectants that express GFP. By subcultures, the transfected hTScells were fixed with methanol (10 min) to detect the expression of GFPin hTS cell transfectants by immunofluorescence. The transfection ratein the present study yielded over 95%.

Rat Model of Parkinsonism and hTS Cells Transplantation

Sprague-Dawley rats (250-350 g) are used in models for 6-OHDA-lesionedhemiparkinsonism (PD). The protocol was approved by the Hospital EthicalCommittee of National Taiwan University Hospital. The surgicalprocedures were described previously. Briefly, after anesthesia bycholral hydrate (4%, 1 cc/100 gm of body weight), stereotaxic lesionswere carried out by infusion of 6-hydroxydopamine (Sigma) into the rightmedian forebrain bundle (AP 2.8/Lat 2.2/Dep 8.0 mm) at a rate of 1μg/0.5 μl/min for 8 min (injection pump: CMA 100). After 10 min, thetube was removed. Two weeks later, apormorphine-induced rotation tests(25 mg/kg, s.c.) were performed 20 min after cells transplantation. Theturning rotations were recorded. Rotations of more than 25 in 5 min wereincluded in the study. Analysis was set at 0, 3, 6, 9, and 12 weeks.Rats were separated into 3 groups: group a was injected with non-inducedbut plasmid-transfected hTS cells; group b with both plasmid-transfectedand induced hTS cells; and group c with PBS injection as control. Cellswere transplanted into 2 sites (each site: 3×10⁶/4 μl) within the rightunilateral striatum (1st site: AP+1/Lat+2.7/Dep 6.4 mm; 2^(nd)site:AP+0/Lat+2.7/Dep 6.4 mm).

The functional assessment in vivo was done to test whether the hTScell-derived neural stem cells play a role in Parkinson's disease (PD).The F1B-GFP reporter plasmid transfected hTS cells were prepared with ayield of over 95% (FIG. 4 a). Using a specific monoclonal antibody fortyrosine hydroxylase-2 or -16 detection, we observedimmunocytochemically the expressions of TH-2 in the induced neural stemcells with a yield >95% (FIGS. 4 b) and TH-16 in the F1B-FGP reporterplasmid transfected hTS cells, with also a yield of >95%, afterinduction (FIG. 4 c, d, e). Animal models of PD are popularly used toassess the effects of neural grafts implanted into the striatum(Dunnett, S. B.& Bjorklund, Nature 399, A32-A39 (1999)) Thus, unilateralinjections of 6-OHDA into median forebrain bundle in rats (FIG. 4 f, g,h, upper panel) permanently damaged all dopaminergic neurons in the SNpars compacta (snc) (lancu, R. et al., Behav Brain Res 162, 1-10 (2005))(FIG. 4 f, g, lower panel). Two weeks later, we implanted both inducedand non-induced transfected hTS cells (FIG. 4 g; FIG. 4 h) into theintrastriatal region. Phosphate buffer solution was used in the controlgroup (FIG. 4 f). Apomorphine-induced rotations were measured asdescribed previously. The results demonstrated that the total number ofcontralateral rotations decreased significantly following thetransplantation of non-induced hTS cells (FIG. 4 k), and finally reducedto the baseline (25 turns/5 min) at 12 weeks (Repeated-measure ANOVAtest: p=0.001). In the retinoic acid-induced group, the best recoverytime was shown at 6 weeks (p<0.05). However, no difference between theinduced and the control groups was observed at 12 weeks. All rats werekilled after 18 weeks. Sections of the rat brains were sent for THimmunohistochemistry, and they also underwent immunocytochemistry fortransfected hTS cells in the nigrostriatal pathway. No TH immunoactivitywas detected in the lesioned striatum and snc of the induced hTS cellgroup or the control groups (FIG. 4 f, g). Of great importance is theunexpected finding that in the non-induced hTS cells group, THimmunoreactivities were found in both the lesioned striatum and sncregions (FIG. 4 h). The appearance of both transfected hTS cells and THimmunoreactivities in the lesioned areas of striatum (FIG. 4 i) and snc(FIG. 4 j) provides direct evidence that the implanted hTS cells can notonly differentiate into dopaminergic neurons in situ, in such a uniquemicro-environment, but also repair the function originally damaged by6-OHDA-lesions. This goes against the accepted notion that6-OHDA-induced lesions are permanent. On the contrary, the hTS cells areable to find the their way home along the nigrostriatal pathway byupstream migration, much as salmon find their way back up the river innature. How this is achieved remains to be clarified. Our findings showthat it is possible to use hTS cells as viable alternatives to hES andhEG cells, thereby circumventing the ethical dilemmas related to use ofembryonic stem cells for human stem cell research and gene-based andcell-based therapies.

Example 6 (A) Methods of Differentiation of hTS Cells into Pancreaticβ-Islet Like Cell

Human trophoblastic villi were obtained from the early ectopic pregnancy(6-8 weeks of gestation) at fallopian tube and human trophoblastic stem(hTS) cells were purified as described previously. For pancreaticβ-islet cells differentiation, a two-step regimen was applied based onthe characteristic glucose-stimulated insulin secretion (Wilcox G., ClinBiochem Rev., 2005; 26:19-39). Briefly, cells (1.4×10⁵) were pre-inducedin basic DMEM medium (5.5 mM glucose, Gibco) containing 1 mMβ-mercaptoethanol (Sigma), 10 mM nicotinamide (Sigma), namely LDMEM-mn,at 37° C., 5% CO₂ for 24 h. For further induction, cells were culturedin HDMEM medium (Gibco) containing 15 mM glucose, 1 mMβ-mercaptoethanol, 10 mM nicotinamide, namely HDMEM-mn.

(B) Evidence of β-Islet-Like Cells Differentiated from the hTS CellsCells Culture

Prior to the induction, hTS cells (1.4×10⁵, PV 07, passage 5) werecultured in basic DMEM medium (Gibco) for two days to reach a stablestatus. The hTS cells appeared in an elongated spindle shape beforepre-induction (FIG. 5 a). Then, the culture medium was changed intoLDMEM-mn for 24 h as pre-induction. Morphologically, the cellsaggregated to from into variable multicystic formation at 6 h (FIG. 5b). The cells' morphology gradually changed from spindle shapes intorounded and/or oval shapes, and eventually toward several scatteredgrape-like clusters (FIG. 5 c) after 24 h pre-induction. When the mediumwas switched into a hyperglycemic status, i.e., HDMEM-mn for 6 h, theisolated grape-shaped cells first appeared at 3 h. The clusters showed atrend to link with each other forming a network after 6 hours incubation(FIG. 5 d). The 6 h induction was applied and attributed to theempirical fact that the hTS cells would die at 8-10 hours in suchhyperglycemic conditions (20-22 mM). These cellular damages are probablyattributed to the effect of glucotoxicity. The isolated grape-likeclusters possibly demonstrate initial stages of pancreaticorganogenesis. The results showed that the differentiated hTS cellspossessed insulin secreting capability, exhibiting characteristicglucose-stimulated insulin secretion after an acute glucose bolusadministration (FIG. 5 h). Meanwhile, small amount of the culture medium(0.5 ml) was collected at several points during the culture andsubjected for insulin determinations by radioimmunoassay usingcommercial kits per manufacturer's directions (Diagnostic ProductsCorp., Los Angeles, Calif.). The result displays a residual trace ofinsulin in the medium after the acute glucose bolus administration,which may reflect the secreting pattern previously observed in humanpancreatic β-islet cells (Jose et al., The Journal of Physiology (1999),520.2, pp. 473-483) that there are two intracellular pools of insulin,i.e., primed and reserved forms.

The cell culture medium was changed back to the basic DMEMS for culturefor 18 h. We discovered that fibroblastic outgrowths appeared from thegrape-like clusters as a result (FIG. 5 e). The de-differentiationphenomena became obvious after 2-, and 4-days culture (FIG. 5 f, g). Themechanism for de-differentiation is still unclear. The differentiationand de-differentiation in cellular morphology are unique and repeatablein the present study.

The findings offer the possibility of using hTS cells as a model in thestudy of not only the patterning of beta-cells in early pancreaticdevelopment, the signaling in differentiated beta-cells of the endocrinepancreas in regulating insulin production, but also the pathogenesis ofthe impaired placental function at molecular levels. In murine, it hasbeen reported recently that parathyroid hormone-related protein canregulate cellular changes in secondary trophoblast giant cells, whichinvade into the uterus at implantation during differentiation(El-Hashash and Kimber, Dev. Biol. 2005 Dec. 19). The result impliesthat insulin may play a role in regulating the cellular changes duringhTS cell differentiation and de-differentiation. Another report revealedthat the Notch pathway plays as a mediator of beta-cellde-differentiation in type 1 diabetes mellitus that inhibited thedifferentiated functions in dividing but not in terminallydifferentiated beta-cells (Darville M I et al., Biochem Biophys ResCommun., 2006;339:1063-8). The de-differentiation phenomenon of the hTScells can possibly be used as a model for further research of the roleof the Notch pathway in type 1 diabetes mellitus. Furthermore, cellularde-differentiation can induce anticancer activity that makes cellsresistant to carcinogenesis (Scott R E et al., Differentiation., 2005;73:294-302), though the molecular mechanism of this phenomenon has notbeen defined. The de-differentiation phenomenon of the hTS cells canalso be applied to the study of the mechanism of cancer.

Insulin-Related Gene Expressions in the Derived β-Islet-Like Cells

To further identify the similarity with human pancreatic β-islet cellsin biological characteristics, the harvested differentiated hTS cellswere examined by genetic expressions in relation to pancreaticneuroendocrine activities using RT-PCR. The primer sequences used wereshown in Table 3.

The methods used were described previously in this context. Theinvestigations included insulin (expressed by β-islet cells), Pdx-1(transcription factor expressed by β-islet cells), somatostatin(expressed by delta-islet cells), CK19 (progenitors of islet and ductalcells), neurogenin (involved in neurogenesis, also a common precursor ofthe 4 pancreatic endocrine cell types), neurofilament (structuralprotein for neuron), nestin (intermediate filament structure protein),CD133 (identified neural stem cells with rising to neuron and glialcells), MAP-2 (dendrite-specific protein), MPB (myelin sheathsurrounding protein produced by oligodendrocytes), GFAP(astrocyte-specific protein) and Oct-4 (transcription factor unique forcell proliferation). The results (FIG. 6) showed that insulin, Pdx-1,neurogenin and nestin expressions appeared after induction. Enhancedexpressions of CK19, somatostatin, neurofilament, CD133, MAP-2, andOct-4 were observed after drug induction in comparison with that ofnon-induced cells. However, GFAP and MPB did not express in this study.These results demonstrated that the differentiated islet-like cellspossess most of the genetic expressions similar to human pancreaticislets as a complex neuroendocrine organ.

TABLE 3 Sequences of primers (SEQ ID NOs 27-48, respectively, in orderof appearance) Product Gene Sequence (5′→3′) (bp) Tm InsulinF: AGCCTTTGTGAACCAACACC 104 60.8 R: CTCACCCTGCAGGTCCTCT Pdx-1F: GTCCTGGAGGAGCCCAAC 360 58 R: GCAGTCCTGCTCAGGCTC Somato-F: CAGGAACTGGCCAAGTAC 186 54.6 statin R: AGTTCTTGCAGCCAGCTTTG CK19F: GCCTCCAAGGTCCTCTGAG 120 63.5 R: GGCAGGTCAGGAGAAGAGC Neuro-F: ACTACATCTGGGCGCTGACT 144 58.1 genin R: GGGAGACTGGGGAGTAGAGG Neuro-F: TGGGAAATGGCTCGTCATTT 332 55.5 filament R: CTTCATGGAAGCGGCCAATT NestinF: CTCTGACCTGTCAGAAGAAT 315 51.8 R: GACGCTGACACTTACAGAAT CD133F: GAGCGCAAAGACTACCTGAAGA 230 57 R: CGACTCTAGCTCGATGCTCTTG MAP-2F: GCATGAGCTCTTGGCAGG 192 55.4 R: CCAATTGAACCCAGTAAAGCC β-actinF: GTGGGGCGCCCCAGGCACCA 539 55.5 R: CTCCTTAATGTCACGCACGATTTC Oct-4F: GGAAAGGCTTCCCCCTCAGGGAAAGG 450 64 R: AAGAACATGTGTAAGCTGCGGCCC

Immunocytochemistry of the Insulin-Related Proteins in the β-Islet-LikeCells

To further verify this notion, the differentiated hTS cells were platedin six-well chamber slides and cultured at 37° C. with humidity at 5%CO₂ for 24 h. After cells adhered to the slide, immunocytochemical studywas performed. The cells were washed with phosphate-buffered saline(PBS), fixed in 4% paraformaldehyde at 4° C. overnight and permeabilizedwith 0.4% Triton X-100 for 20 min. To reduce non-specific antibodybinding, cells were first pre-incubated with a blocking buffer (10% BSAin PBS) for 20 minutes before incubation with primary antibodies. A goatanti-insulin (1:100 dilution, Santa Cruz), a rabbit anti-glucagon (1:50dilution, Santa Cruz), a goat anti-IGF1 (1:50 dilution, Santa Cruz), amouse anti-tau (1:50 dilution, Santa Cruz), a goat anti-MAP-2 (1:50dilution, Santa Cruz), and a goat anti-amylase (1:50 dilution, SantaCruz) were applied for 60 min. After washing with PBS-Tween 20 bufferfor 5 min three times each, secondary anti-goat IgG Texas red-conjugatedantibody (1:500, dilution, Santa Cruz) and anti-rabbit IgGFITC-conjugated antibody (1:500 dilution, Santa Cruz), anti-goat IgGFITC-conjugated antibody (1:500, dilution, Santa Cruz) and anti-mouseIgG FITC-conjugated antibody (1:500, dilution, Santa Cruz) were appliedfor 60 min. After washing with PBS-Tween 20 buffer for 5 min threetimes, the cells were counterstained with 100 ng/ml DAPI (Sigma) for 10min to identify the nucleus. The immunoreactivities were analyzed byusing a fluorescent microscope (Provis, Olympus). The results confirmedthat hTS cells can differentiate into pancreatic islet-like cells withpositive immunoreactive expressions of insulin, insulin-like growthfactor-1 (IGF-1), glucagon, amylase, tau and MAP-2 (FIG. 7).

(C) Establishment of 3-D Pancreatic β-Islet Tissues Using a CollagenModel In Vitro

Based on the morphological observations during cell culture, we becameaware of the fact that sudden changes from the low (5.5 mM) to high (15mM) glucose levels probably resulted in stress to the hTS cells. Toavoid this side-effect, we applied a culture system using mixed collagengels as matrices in a Transwell dish (Corning Incorp., Corning, N.Y.)for two reasons: one is to explore hTS cells' invasive capability duringproliferation and the other is to find out the possibility of promotingpancreatic islet-like tissue growth on the gel matrix during induction.Thus, collagen mixtures of vitrogen collagen (1:5 dilution, Cohesion,Palo Alto. CA) and collagen from rat tail (3 mg/ml of buffer solution,c7661, Sigma) at a ratio of 1:1 (v/w) in acidic solution (0.012 N HC1)were prepared and coated (1.5 ml) onto the upper chamber of theTranswell dish for 20-30 min form a gel layer. For testing, HDMEN-mnmedium (18 mM glucose) was placed in the lower chamber of the Transwelldish (2.4 cm diameter, 0.4 μm pore size), while LDMEN-mn (5.5 mMglucose) was placed in the upper chamber. For pre-test, the equilibriumof glucose concentration was achieved at a level around 455 mg/dl at 4 htest. Thus, we implanted the induced and non-induced hTS cells (5×10⁵cells) on the collagen gel and transferred to the Transwell described asabove for examination. The drug induced hTS cells (FIG. 8 a) and thenon-drug-induced control (FIG. 8 b) both achieved equilibrium of glucoselevels at 4 h. Both cell-embedded collagen mixtures formed a 3-Dcellular mass (FIG. 8 c). Both culture mediums were collected andinsulin level was determined by radioimmunoassays. Each gel mass wasfixed in 4% paraformaldehyde overnight at 4° C. and subjected forinsulin immunohistochemistry.

Histologically, in the non-drug-induced control gel mass, proliferationof spindle cells showing hyperchromatic nuclei and presence of nucleolias well as cytoplasmic vacuoles, revealed an immature feature around 10cell-layers with rich extra-cellular matrices and stratification inthin, sheet-like appearance (FIG. 9 a). The cells appear verticallyarranged. The surface appeared in a flat, umbrella-like layer. The cellsin the middle zone were randomly and irregularly arranged. The cells inthe lower zone towards the collagen showed vertical formations,indicating penetration into the collagen.

However, in the gel mass of the drug-induced hTS cells, the cellcomponents became more compact and well-differentiated, evidenced by thereduced cytoplasmic vacuoles and the amount of cellular matrix (FIG. 9b). The mechanism for this 3-D formation is unclear. However, recentresearch revealed that insulin-like growth factor-1 can stimulatelamellipodia formation and promote adhesion of trophoblast cells toextracellular matrix by activating their adhesion molecules that must beactivated within the implantation window (Kabir-Salmani et al., 2002).In this study, immunoreactive insulin levels in the total culture mediumwere measured by radioimmunoassays with a range of 15-27 mIU/ml.

Immunohistochemically, no insulin-staining granules were visible in thecytoplasm of the cells in the non-drug-induced hTS cells (FIG. 9 c).However, it expressed apparently in the drug-induced hTS cells (FIG. 9d). Tissues from normal pancreas (FIG. 9 e) and insulinoma (FIG. 5 f)were obtained and used as positive control. More importantly, this factprovides evidence that the hTS cells are able to form pancreaticislet-like tissues in vitro, suggesting the possibility to producepancreatic β-islet tissues for future clinical applications in humanswith type 1 diabetes mellitus.

Evidence was found that hTS cells may differentiate into pancreaticislet-like cells with insulin-secreting capability. The uniquebiological characteristics of hTS cells in differentiation andde-differentiation in combination with the present 3-D cellular modelmight be used as platforms for: (1) the research for understanding themechanisms in any differentiated cell phenotypes. For example, researchin pancreatic development of type 1 diabetes mellitus, evaluating theeffects of drugs in early embryonic implantation, development ofplacental functions in relation to placental insufficiency, gestationaldiabetes mellitus, macrosomnia, early pregnancy loss, geneticabnormalities, and choriocarcinoma; and (2) the establishment ofpancreatic tissues and/or organs which may one day help to provide asource of islets for use in transplantation therapy to treat type 1diabetes.

While the invention has been described and exemplified in sufficientdetail for those skilled in this art to make and use it, variousalternatives, modifications, and improvements should be apparent withoutdeparting from the spirit and scope of the invention.

One skilled in the art readily appreciates that the present invention iswell adapted to carry out the objects and obtain the ends and advantagesmentioned, as well as those inherent therein. The embryos, animals, andprocesses and methods for producing them are representative of preferredembodiments, are exemplary, and are not intended as limitations on thescope of the invention. Modifications therein and other uses will occurto those skilled in the art. These modifications are encompassed withinthe spirit of the invention and are defined by the scope of the claims.

Thus, while there have shown and described and pointed out fundamentalnovel features of the invention as applied to a preferred embodimentthereof, it will be understood that various omissions and substitutionsand changes in the form and details of the devices illustrated, and intheir operation, may be made by those skilled in the art withoutdeparting from the spirit of the invention. For example, it is expresslyintended that all combinations of those elements and/or method stepswhich perform substantially the same function in substantially the sameway to achieve the same results are within the scope of the invention.Moreover, it should be recognized that structures and/or elements and/ormethod steps shown and/or described in connection with any disclosedform or embodiment of the invention may be incorporated in any otherdisclosed or described or suggested form or embodiment as a generalmatter of design choice. It is the intention, therefore, to be limitedonly as indicated by the scope of the claims appended hereto.

What is claimed is: 1-42. (canceled)
 43. A method of screening for atherapeutic that modulates human trophoblast stem cell differentiationor activity, comprising; a. subjecting a human trophoblast stem cell toa test substance; and b. evaluating the effect of the test substance todetermine if the test substance modulates differentiation or activity ofthe human trophoblast stem cell, wherein the human trophoblast stem cellexpresses Octainer-4 (Oct4) and SSEA-4.
 44. The method of claim 43,wherein the test substance is a therapeutic compound.
 45. The method ofclaim 44, wherein the therapeutic compound is a drug, a chemical, or anantibody.
 46. The method of claim 45, wherein the therapeutic compoundis an immunosuppressive agent or a supportive agent.
 47. The method ofclaim 43, wherein the test substance modulates bFGF. Oct 4, FGFR-2. orFGF4,
 48. The method of claim 47, wherein the test substance is aninhibitor of bFGF, Oct 4, FGFR-2, or FGF4.
 49. The method of claim 43,wherein the human trophoblast stem cell is capable of forming embryonicbodies with an adhesive characteristic.
 50. The method of claim 43,wherein the human trophoblast stem cell is capable of maintaining thelength of chromosomal telomeres in passages in culture.
 51. The methodof claim 43, wherein the human trophoblast stein cell is capable ofdifferentiating into a mesenchymal cell expressing cell surface markersCD44 or CD90.
 52. The method of claim 43, wherein the human trophoblaststem cell is capable of differentiating into an endodermal, mesodermal,and/or ectodermal cell.
 53. The method of claim 43, wherein the humantrophoblast stem cell is capable of differentiating into an osteoblast,chondrocyte, myocyte, adipocyte, neural cell, pancreatic islet stemcell, or progenitor cell.
 54. The method of claim 43, wherein the humantrophoblast stem cell has a gene switching mechanism that isbFGF-dependent.
 55. The method of claim 43, wherein the humantrophoblast stem cell is genetically modified to introduce a mutationinto the cell.
 56. The method of claim 43, wherein the human trophoblaststem cell produces a growth factor or a hormone.
 57. The method of claim56, wherein the hormone is human chorionic gonadotropin (hCG).